U.S. patent application number 12/712159 was filed with the patent office on 2011-08-25 for lead frame and semiconductor package manufactured therewith.
This patent application is currently assigned to FREESCALE SEMICONDUCTOR, INC. Invention is credited to Yin Kheng Au, Mohd Rusli Ibrahim, Meng Kong Lye, Kesyakumar V.C. Muniandy, Zi Song Poh, Seng Kiong Teng.
Application Number | 20110204498 12/712159 |
Document ID | / |
Family ID | 44475807 |
Filed Date | 2011-08-25 |
United States Patent
Application |
20110204498 |
Kind Code |
A1 |
Au; Yin Kheng ; et
al. |
August 25, 2011 |
LEAD FRAME AND SEMICONDUCTOR PACKAGE MANUFACTURED THEREWITH
Abstract
A lead frame for a semiconductor package has a flag to which a
semiconductor die is mounted. Tie bars are coupled to the flag.
There is a first set of leads and each first set lead in the first
set of leads has a first set lead parallel length and a first set
lead tapered length. The first set lead parallel length of each
first set lead has a constant width and edges that are parallel to
edges of all other first set lead parallel lengths. A free end
region of the first set lead tapered length of each first set lead
provides a first set lead bond target region. There is a second set
of leads disposed between a first one of the tie bars and the first
set of leads. Each second set lead, in the second set of leads, has
a second set lead parallel length and a second set lead tapered
length. The second set lead parallel length of each second set lead
has a constant width and edges that are parallel to edges of all
other second set lead parallel lengths in the second set of leads
and also parallel to the edges of first set lead parallel lengths.
At least one second set lead has an extension length extending
inwardly from the second set lead tapered length, the extension
length has a constant width and provides a second set lead bond
target region. Wire bond leads electrically couple both the first
set lead bond target region and second set lead bond target region
to respective die external electrical connection pads on a surface
of the die and a package body encloses the die.
Inventors: |
Au; Yin Kheng; (Petaling
Jaya, MY) ; Ibrahim; Mohd Rusli; (Shah Alam, MY)
; Lye; Meng Kong; (Shah Alam, MY) ; Poh; Zi
Song; (Petaling Jaya, MY) ; Teng; Seng Kiong;
(Kemuning Utama, MY) ; Muniandy; Kesyakumar V.C.;
(Klang, MY) |
Assignee: |
FREESCALE SEMICONDUCTOR,
INC
Austin
TX
|
Family ID: |
44475807 |
Appl. No.: |
12/712159 |
Filed: |
February 24, 2010 |
Current U.S.
Class: |
257/670 ;
257/676; 257/E23.031; 257/E23.032 |
Current CPC
Class: |
H01L 2924/00014
20130101; H01L 2224/48247 20130101; H01L 24/48 20130101; H01L
2924/00014 20130101; H01L 24/49 20130101; H01L 2924/00014 20130101;
H01L 2224/45099 20130101; H01L 2924/207 20130101; H01L 2224/45015
20130101; H01L 23/49541 20130101; H01L 2924/181 20130101; H01L
2224/49171 20130101; H01L 2924/00 20130101; H01L 2224/48247
20130101; H01L 2924/00012 20130101; H01L 2224/05554 20130101; H01L
2924/181 20130101; H01L 2224/49171 20130101 |
Class at
Publication: |
257/670 ;
257/676; 257/E23.031; 257/E23.032 |
International
Class: |
H01L 23/495 20060101
H01L023/495 |
Claims
1. A lead frame comprising: a lead frame flag; tie bars coupling
the lead frame flag to an outer boundary of the lead frame; a first
set of leads extending from the outer boundary towards the lead
frame flag, each first set lead in the first set of leads having a
first set lead parallel length adjacent the outer boundary and a
first set lead tapered length extending inwardly from an end of the
first set lead parallel length, the first set lead parallel length
of each first set lead having a constant width and edges that are
parallel to edges of all other first set lead parallel lengths in
the first set of leads, wherein a free end region of the first set
lead tapered length of each first set lead provides a first set
lead bond target region; and a second set of leads disposed between
a first one of the tie bars and the first set of leads, each second
set lead in the second set of leads having a second set lead
parallel length adjacent the outer boundary and a second set lead
tapered length extending inwardly from an end of the second set
lead parallel length, the second set lead parallel length of each
second set lead having a constant width and edges that are parallel
to edges of all other second set lead parallel lengths in the
second set of leads and also parallel to the edges of first set
lead parallel lengths, wherein at least one second set lead has an
extension length extending inwardly from the second set lead
tapered length, the extension length having a constant width and
providing a second set lead bond target region.
2. The lead frame of claim 1, wherein the second set lead bond
target region of each second set lead is closer to the lead frame
flag than the first set lead bond target region of each first set
lead.
3. The lead frame of claim 2, wherein the extension length is in a
direction extending away from the first one of the tie bars.
4. The lead frame of claim 3, wherein the extension length is at an
angle relative to the second set lead tapered length.
5. The lead frame of claim 2, wherein the extension length is in a
direction extending towards the first one of the tie bars.
6. The lead frame of claim 5, wherein the extension length is at an
angle relative to the second set lead tapered length.
7. The lead frame of claim 2, wherein the second set lead parallel
length is at an angle relative to the second set lead tapered
length.
8. The lead frame of claim 2, wherein the first set lead parallel
length is at an angle relative to the first set lead tapered
length.
9. The lead frame of claim 2, wherein each first set lead bond
target region of each first set lead are equidistant from the lead
frame.
10. The lead frame of claim 2, wherein a minimum wire bond distance
between the lead frame and second set lead bond target differs for
each second set lead, wherein the closer the second set lead is to
the first one of the tie bars the smaller is the minimum respective
bond target distance.
11. A semiconductor package comprising: a lead frame flag; a
semiconductor die mounted to the lead frame flag; tie bars coupled
to the lead frame flag; a first set of leads extending from an
outer boundary of the semiconductor package towards the lead frame
flag, each first set lead in the first set of leads having a first
set lead parallel length adjacent the outer boundary and a first
set lead tapered length extending inwardly from an end of the first
set lead parallel length, the first set lead parallel length of
each first set lead having a constant width and edges that are
parallel to edges of all other first set lead parallel lengths in
the first set of leads, wherein a free end region of the first set
lead tapered length of each first set lead provides a first set
lead bond target region; and a second set of leads disposed between
a first one of the tie bars and the first set of leads, each second
set lead in the second set of leads having a second set lead
parallel length adjacent the outer boundary and a second set lead
tapered length extending inwardly from an end of the second set
lead parallel length, the second set lead parallel length of each
second set lead having a constant width and edges that are parallel
to edges of all other second set lead parallel lengths in the
second set of leads and also parallel to the edges of first set
lead parallel lengths, wherein at least one second set lead has an
extension length extending inwardly from the second set lead
tapered length, the extension length having a constant width and
providing a second set lead bond target region; wire bond leads
electrically coupling both the first set lead bond target region
and second set lead bond target region to respective die external
electrical connection pads on a surface of the die; and a package
body enclosing the die.
12. The semiconductor package of claim 11, wherein the second set
lead bond target region of each second set lead is closer to the
lead frame flag than the first set lead bond target region of each
first set lead.
13. The semiconductor package of claim 12, wherein the extension
length is in a direction extending away from the first one of the
tie bars.
14. The semiconductor package of claim 13, wherein the extension
length is at an angle relative to the second set lead tapered
length.
15. The semiconductor package of claim 12, wherein the extension
length is in a direction extending towards the first one of the tie
bars.
16. The semiconductor package of claim 15, wherein the extension
length is at an angle relative to the second set lead tapered
length.
17. The semiconductor package of claim 12, wherein the second set
lead parallel length is at an angle relative to the second set lead
tapered length.
18. The semiconductor package of claim 12, wherein the first set
lead parallel length is at an angle relative to the first set lead
tapered length.
19. The semiconductor package of claim 12, wherein each first set
lead bond target region of each first set lead are equidistant from
the lead frame.
20. The semiconductor package of claim 12, wherein a minimum wire
bond distance between the lead frame and second set lead bond
target differs for each second set lead, wherein the closer the
second set lead is to the first one of the tie bars the smaller is
the minimum respective bond target distance.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to lead frames and
semiconductor packages. The present invention is particularly
suited to lead frames and semiconductor packages associated with
wire bonding of leads of the lead frame to external connection die
pads of a semiconductor die.
[0002] Typical packaged semiconductors are formed with a
semiconductor die mounted to a lead-frame. The lead-frame is formed
from a sheet of metal that comprises a flag and tie bars attach the
flag to an outer boundary of the frame. Each of the tie bars are
bent so that the frame and flag are in different planes, this is
often referred to as the flag being "down-set".
[0003] Bond targets on leads of the lead-frame are wire bonded to
external connection die pads to thereby provide a means of easily
electrically connecting the die to circuit boards and the like.
After the external connection die pads and bond targets are wire
bonded, by bonding wires, the semiconductor die and pads are
encapsulated (packaged) in a compound such as a plastics material
leaving only sections of the leads exposed. These exposed leads are
cut from the frame of the lead-frame (singulated) and bent for ease
of connection to a circuit board.
[0004] It is well known that the number of transistors on a
semiconductor die is continuously increasing. This increase results
in greater die functionality and the need for more external
connection die pads. The external connection die pads are generally
disposed in along perimeter edges of the die and as their number
increases problems can occur with wire bonding. Specifically, the
width and density of the leads limit the proximity of the bond
targets to the die pads. Accordingly, as the number of die pads
increases the distance between the dies pads and bond targets also
increases. As a result, longer bonding wires are required that may
cause wire sweep, or wire shorting, especially for bonding wires
that are bonded to bond targets near the ties bars where the bond
wire length is typically the longest and space is lead space is
limited due to the tie bars.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] The invention, together with objects and advantages thereof,
may best be understood by reference to the following description of
preferred embodiments together with the accompanying drawings in
which:
[0006] FIG. 1 is a plan view of a lead frame in accordance with a
preferred embodiment of the present invention;
[0007] FIG. 2 is a plan view of a semiconductor package
manufactured from the lead frame of FIG. 1;
[0008] FIG. 3 is a side view of the semiconductor package of FIG.
2;
[0009] FIG. 4 is a plan view of a lead frame in accordance with
another preferred embodiment of the present invention; and
[0010] FIG. 5 is a plan view of a semiconductor package
manufactured from the lead frame of FIG. 4.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0011] The detailed description set forth below in connection with
the appended drawings is intended as a description of presently
preferred embodiments of the invention, and is not intended to
represent the only forms in which the present invention may be
practiced. It is to be understood that the same or equivalent
functions may be accomplished by different embodiments that are
intended to be encompassed within the spirit and scope of the
invention. In the drawings, like numerals are used to indicate like
elements throughout. Furthermore, terms "comprises," "comprising,"
or any other variation thereof, are intended to cover a
non-exclusive inclusion, such that system, circuit, device
components and method steps that comprises a list of elements or
steps does not include only those elements but may include other
elements or steps not expressly listed or inherent to such system,
circuit, device components or steps. An element or step proceeded
by "comprises . . . a" does not, without more constraints, preclude
the existence of additional identical elements or steps that
comprises the element or step.
[0012] In one embodiment the present invention provides a lead
frame comprising a lead frame flag and tie bars coupling the lead
frame flag to an outer boundary of the lead frame. There is a first
set of leads extending from the outer boundary towards the lead
frame flag, each first set lead in the first set of leads has a
first set lead parallel length adjacent the outer boundary and a
first set lead tapered length extending inwardly from an end of the
first set lead parallel length. The first set lead parallel length
of each first set lead has a constant width and edges that are
parallel to edges of all other first set lead parallel lengths in
the first set of leads. A free end region of the first set lead
tapered length, of each first set lead, provides a first set lead
bond target region. There is a second set of leads disposed between
a first one of the tie bars and the first set of leads. Each second
set lead, in the second set of leads, has a second set lead
parallel length adjacent the outer boundary and a second set lead
tapered length extending inwardly from an end of the second set
lead parallel length. The second set lead parallel length of each
second set lead has a constant width and edges that are parallel to
edges of all other second set lead parallel lengths in the second
set of leads and also parallel to the edges of first set lead
parallel lengths. At least one second set lead has an extension
length extending inwardly from the second set lead tapered length,
the extension length has a constant width and provides a second set
lead bond target region.
[0013] In another embodiment the present invention provides a
semiconductor package comprising a lead frame flag and a
semiconductor die mounted to the lead frame flag. Tie bars are
coupled to the lead frame flag and there is a first set of leads
extending from an outer boundary of the semiconductor package
towards the lead frame flag. Each first set lead in the first set
of leads has a first set lead parallel length adjacent the outer
boundary and a first set lead tapered length extending inwardly
from an end of the first set lead parallel length. The first set
lead parallel length of each first set lead has a constant width
and edges that are parallel to edges of all other first set lead
parallel lengths in the first set of leads. A free end region of
the first set lead tapered length of each first set lead provides a
first set lead bond target region. There is a second set of leads
disposed between a first one of the tie bars and the first set of
leads. Each second set lead, in the second set of leads, has a
second set lead parallel length adjacent the outer boundary and a
second set lead tapered length extending inwardly from an end of
the second set lead parallel length. The second set lead parallel
length of each second set lead has a constant width and edges that
are parallel to edges of all other second set lead parallel lengths
in the second set of leads and also parallel to the edges of first
set lead parallel lengths. At least one second set lead has an
extension length extending inwardly from the second set lead
tapered length, the extension length has a constant width and
providing a second set lead bond target region. Wire bond leads
electrically couple both the first set lead bond target region and
second set lead bond target region to respective die external
electrical connection pads on a surface of the die and a package
body encloses the die.
[0014] Referring to FIG. 1 there is illustrated a plan view of a
lead frame 100 in accordance with a preferred embodiment of the
present invention. The lead frame 100 includes a lead frame flag
105 and there are tie bars 110,111,112,113 coupling the lead frame
flag 105 to an outer boundary 115 of the lead frame 100. More
specifically, the lead frame flag 105 is typically substantially
rectangular and the tie bars 110,111,112,113 extend from corner
areas 120 of the lead frame flag 105. The lead frame 100 has a
first set of leads 125 extending from the outer boundary 115
towards the lead frame flag 105. Each first set lead 130, in the
first set of leads 125, has a first set lead parallel length 135
adjacent the outer boundary 115 and a first set lead tapered length
140 extending inwardly from an end of the first set lead parallel
length 135. The first set lead parallel length 135 of each first
set lead 130 has a constant width and edges that are parallel to
edges of all other first set lead parallel lengths 135 in the first
set of leads 125. Also, a free end region of the first set lead
tapered length 140 of each first set lead 130 provides a first set
lead bond target region 150.
[0015] There is a second set of leads 155 disposed between a first
one of the tie bars 110 and the first set of leads 125. Each second
set lead 160, in the second set of leads 155, has a second set lead
parallel length 165 adjacent the outer boundary and a second set
lead tapered length 170 extending inwardly from an end of the
second set lead parallel length 165. The second set lead parallel
length 165 of each second set lead 160 has a constant width and
edges 175 that are parallel to edges 175 of all other second set
lead parallel lengths 165 and also parallel to the edges 140 of the
first set lead parallel lengths 135. Furthermore, at least one (and
typically most or every) second set lead 160 has an extension
length 180 extending inwardly from the tapered length 170. This
extension length 180 has a constant width and provides a second set
lead bond target region 185.
[0016] As illustrated, the second set lead bond target region 185
of each second set lead 160 is closer to the lead frame flag 105
than the first set lead bond target region 150 of each first set
lead 125. Also, with the exception of the second set lead 160 that
is immediately adjacent the first one of the tie bars 110, the
extension length 180 is in a direction extending away from the
first one of the tie bars 110 at an angle relative to the second
set lead tapered length 170. In addition, the second set lead
parallel length 165 of every second set lead 160 is at an angle
relative to the second set lead tapered length 170. Similarly, the
first set lead parallel length 135 of every first set lead 130 is
at an angle relative to the first set lead tapered length 140.
[0017] In this embodiment, each first set lead bond target region
150 of each first set lead 130 are equidistant from the lead frame
105. The distance of each first set lead bond target region 150 is
indicated by arrow line L. Also, a minimum wire bond distance,
indicated by line M, between the lead frame 105 and second set lead
bond target 185 differs for each second set lead 160. In this
regard, the closer the second set lead 160 is to the first one of
the tie bars 110 the smaller is the minimum respective bond target
distance M.
[0018] It is clear from the illustration of FIG. 1 that there also
another second set of leads 155 disposed between a second one of
the tie bars 111 and the first set of leads 125. Also, there is
another first set of leads 125 and two sets of the second set of
leads 155 disposed between the second one of the tie bars 111 and a
third one of the tie bars 112. Similarly, there is another first
set of leads 125 and two sets of the second set of leads 155
disposed between the third one of the tie bars 112 and a fourth one
of the tie bars 113. Finally, there is another first set of leads
125 and two sets of the second set of leads 155 disposed between
the fourth one of the tie bars 112 and the first one of the tie
bars 110. The lead frame flag 105 is "down-set" so that it is in a
different (lower) plane than the first set of leads 125 and second
set of leads 155. The lead frame flag 105 is "down-set" by a bend
190 in each of the in the tie bars 110, 111, 112, 113.
[0019] Referring to FIG. 2 there is illustrated a plan view of a
semiconductor package 200. The semiconductor package 200 includes
the lead frame 100 that has been singulated (cut away) from a
surrounding integral metal sheet (typically copper) that provides
the outer boundary 115. Hence, the outer boundary is now an outer
boundary 205 of the semiconductor package 200 which is simply the
outermost ends of the first and second set of leads 125, 155 and
every first set lead 130 and every second set lead 160 is
electrically separated from all other leads. It will therefore be
apparent that the outer boundary 115 of the lead frame 100 and the
outer boundary 205 of the semiconductor package 200 are
interchangeable depending whether or not reference is being made to
the lead frame 100 or semiconductor package 200. Also, the ties
bars 110,111,112,113 are still coupled to the lead frame flag 105
but have been singulated and therefore electrically isolated from
all leads of the first and second set of leads 125, 155.
[0020] The semiconductor package 200 includes a semiconductor die
210 mounted to the lead frame flag 105. There are wire bond leads
215 electrically coupling both the first set lead bond target
region and second set lead bond target region to respective die
external electrical connection pads 220 on a surface 225 of the die
210. In addition, there is a package body 230 (shown in phantom)
enclosing the die 210, lead frame flag 105, wire bond leads 215,
ties bars 110,111,112,113 and part of the first and second set of
leads 125, 155. However, the majority of the parallel lengths 135
and 165 extend outside the package body.
[0021] Referring to FIG. 3 there is illustrated a side view of the
semiconductor package 200. As shown, the parallel lengths 135 and
165 are bent to provide contact pads (feet) 305 that form a seating
plane X.
[0022] Referring to FIG. 4 there is illustrated a plan view of a
lead frame 400 in accordance with another preferred embodiment of
the present invention. The lead frame 400 includes a lead frame
flag 405 and there are tie bars 410,411,412,413 coupling the lead
frame flag 405 to an outer boundary 415 of the lead frame 400. More
specifically, the lead frame flag 405 is typically substantially
rectangular and the tie bars 410,411,412,413 extend from corner
areas 420 of the lead frame flag 405. The lead frame 400 has a
first set of leads 425 extending from the outer boundary 415
towards the lead frame flag 405. Each first set lead 430, in the
first set of leads 425, has a first set lead parallel length 435
adjacent the outer boundary 415 and a first set lead tapered length
440 extending inwardly from an end of the first set lead parallel
length 435. The first set lead parallel length 435 of each first
set lead 430 has a constant width and edges that are parallel to
edges of all other first set lead parallel lengths 435 in the first
set of leads 425. Also, a free end region of the first set lead
tapered length 440 of each first set lead 430 provides a first set
lead bond target region 450.
[0023] There is a second set of leads 455 disposed between a first
one of the tie bars 410 and the first set of leads 425. Each second
set lead 460, in the second set of leads 455, has a second set lead
parallel length 465 adjacent the outer boundary and a second set
lead tapered length 470 extending inwardly from an end of the
second set lead parallel length 465. The second set lead parallel
length 465 of each second set lead 460 has a constant width and
edges 475 that are parallel to edges 475 of all other second set
lead parallel lengths 465 and also parallel to the edges 440 of the
first set lead parallel lengths 435. Furthermore, at least one (and
typically most or every) second set lead 460 has an extension
length 480 extending inwardly from the tapered length 470. This
extension length 480 has a constant width and provides a second set
lead bond target region 485.
[0024] As illustrated, the second set lead bond target region 485
of each second set lead 460 is closer to the lead frame flag 405
than the first set lead bond target region 450 of each first set
lead 425. Also, with the exception of the second set lead 460 that
is immediately adjacent the first one of the tie bars 410, the
extension length 480 is in a direction extending towards the first
one of the tie bars 410 at an angle relative to the second set lead
tapered length 470. In addition, the second set lead parallel
length 465 of every second set lead 460 is at an angle relative to
the second set lead tapered length 470. Similarly, the first set
lead parallel length 435 of every first set lead 430 is at an angle
relative to the first set lead tapered length 440.
[0025] In this embodiment, each first set lead bond target region
450 of each first set lead 430 are equidistant from the lead frame
405. The distance of each first set lead bond target region 450 is
indicated by arrow line L. Also, a minimum wire bond distance,
indicated by line M, between the lead frame 405 and second set lead
bond target 485 differs for each second set lead 460. In this
regard, the closer the second set lead 460 is to the first one of
the tie bars 410 the smaller is the minimum respective bond target
distance M.
[0026] As illustrated, there also another second set of leads 455
disposed between a second one of the tie bars 411 and the first set
of leads 425. Also, there is another first set of leads 425 and two
sets of the second set of leads 455 disposed between the second one
of the tie bars 411 and a third one of the tie bars 412. Similarly,
there is another first set of leads 425 and two sets of the second
set of leads 455 disposed between the third one of the tie bars 412
and a fourth one of the tie bars 413. Also, there is yet a further
first set of leads 425 and two sets of the second set of leads 455
disposed between the fourth one of the tie bars 412 and the first
one of the tie bars 410.
[0027] Referring to FIG. 5 there is illustrated a plan view of a
semiconductor package 500. The semiconductor package 500 includes
the lead frame 400 that has been singulated and the outer boundary
is now an outer boundary 505 of the semiconductor package 500 which
is simply the outermost ends of the first and second set of leads
425, 455. As a result of singulation, every first set lead 430 and
every second set lead 460 is electrically separated from all other
leads. It will therefore be apparent that the outer boundary 415 of
the lead frame 400 and the outer boundary 505 of the semiconductor
package 500 are interchangeable depending whether or not reference
is being made to the lead frame 400 or semiconductor package 500.
Also, the ties bars 410,411,412,413 are still coupled to the lead
frame flag 405 but have been singulated and therefore electrically
isolated from all leads of the first and second set of leads 425,
455.
[0028] The semiconductor package 500 includes a semiconductor die
510 mounted to the lead frame flag 405. There are wire bond leads
515 electrically coupling both the first set lead bond target
region and second set lead bond target region to respective die
external electrical connection pads 520 on a surface 525 of the die
510. In addition, there is a package body 530 (shown in phantom)
enclosing the die 510, lead frame flag 405, wire bond leads 515,
ties bars 410,411,412,413 and part of the first and second set of
leads 425, 455. As above, the majority of the parallel lengths 435
and 465 extend outside the package body, these parallel lengths 435
and 465 are bent to provide contact pads (feet) 405 that form a
seating plane.
[0029] Advantageously, the present invention alleviates the
requirement of longer bonding wires and may reduce the possibility
of wire sweep or wire shorting of bonding wires that are bonded to
bond targets near the ties bars. These bond targets near the ties
bars are provided by the second set lead bond target region 185 or
485 that are closer to the lead frame flag 405 than the first set
lead bond target region 150 or 450. Also, the problem of limited
lead space due to the tie bars is alleviated since the extension
length 180 or 480 is in either a direction extending towards or
away from the first one of the tie bars.
[0030] The description of the preferred embodiments of the present
invention has been presented for purposes of illustration and
description, but is not intended to be exhaustive or to limit the
invention to the forms disclosed. It will be appreciated by those
skilled in the art that changes could be made to the embodiments
described above without departing from the broad inventive concept
thereof. It is understood, therefore, that this invention is not
limited to the particular embodiment disclosed, but covers
modifications within the spirit and scope of the present invention
as defined by the appended claims.
* * * * *